This invention relates to grooved elastomeric covered rolls and more particularly to a vented or grooved roll cover for use in the paper industry.
In the papermaking process, and for example in the press area of a papermaking machine, rolls having a resilient outer cover and circumferentially extending grooves are used in conjunction with another mating roll or other backing surface or means for pressing or squeezing a web of material such as paper. In this operation, it is important that the roll cover be resilient enough to avoid marking or damage to the web of paper or other material passing therebetween and to avoid damage to the roll cover in case small foreign bodies happen to pass between the rolls.
The roll cover, however, must also be capable of supporting large amounts of pressure in the nip in order to squeeze or press the web of material. The problem, however, becomes even more difficult since it is necessary that the circumferential grooves remain open in order to provide the proper venting action and to provide for the removal of water through the grooves.
The problem which frequently occurs involves the flattening or squeezing of the ribs as they pass through the nip area to such an extent that they widen out in directions transversely of the roll and effectively close up or restrict the grooves. Solutions in the past tended to involve either making the resilient material harder or the grooves wider. Each of these proposals, however, has its limitations since if the grooves become wider or the material harder, there is more tendency to mark or damage the material passing through the nip.